The present invention relates to hydroelectric apparatus and more particularly to a manufacturing process to make a ball valve which is capable of rapidly and precisely to make shape of a ball valve.
As we know that the ball valve is popularly used to the switches. The manufacturing process of the ball valve is categorized as forging, punching and/or roller ramming. FIG. 10 shows a prior art manufacturing process of a ball valve 70 which is adapting the roller ramming process by forging a pair of semi-spherical shapes 71 and welding them together into a ball shape and then making a central passageway by a punching bar. However, this process costs more than others because it has to deal with epidermis chemical disposal and the spherical trimming procedure. Besides, the residual chemical remained on the surface of the ball valve may harm human health. So that this process is now being abandoned.
FIGS. 11, 12 and 13 indicate another prior art process which is adapted a steel plate 81 and punches the steel plate 81 into pieces of small arcuate sheet 81′ at first, secondly, punches the small arcuate sheet 81′ into a large arcuate sheet 81″ and then presses the large arcuate sheets 81′ into the hemi-spherical shapes 80 by an upper and a lower molds. Finally, weld their coupling rims 82 together on pair by pair basis. This process is somewhat complicated due to its repeated punching activities and has to weld the hemispherical shapes together before removing of the upper and lower molds.
FIGS. 14 to 17 show still another prior art process which punches a plate into a cup shaped semi-finished product 91 at first and punches the semi-finished products into a similar spherical shapes 92. Then make an upper, a lower openings 921 and a lateral through hole 922 by punching or drill method. Due to that the openings 921 punched by the upper and lower molds may create protrudent stripes and the lower rim of the cup shape semi-finished product becomes thinner than the other portions of the ball valve that causes the ball valve in uneven thickness in addition to that the protrudent stripes are to be dealt with. So that this process always cause great defective proportion, than other process.
Referring to FIGS. 18 to 22, a further prior art process of manufacturing a ball valve is shown. This process is to punch a plate 1 into a hollow cylindrical shape 2 and a flap 3 which must be removed later, to accomplish a hollow cylindrical shape 2 and a bottom 2001 which is then cut off to remain the hollow cylindrical shape 2 only, next step is to make the cylindrical shape 2 into a ball shape 4 by roller ramming method. Finally makes a rectangular through hole 5 in a periphery of the ball shape 4. So that a ball valve is therefore finished. However, this process requires twice cutting procedures and the thickness of the ball is not so even. Besides, the circular measure is always not symmetrical such that the result is not qualified.
The above discussed prior art manufacturing processes have a common disadvantage that the connection hole for linking a valve stem is punched after the configuring of the ball valve that may cause a deformation of the ball valve that not only affects a perfect connection of the valve stem with the ball valve but also face the leakage of the water and/or the air.